RAISING BLOOD PRESSURE — COUNTING PULSE. 293 



Mode of Baising Blood-jpressurc. — This may be done either by 

 injecting a sufficient quantity of the defibrinated blood of 

 another animal of the same species, warmed to 98° Fahr., 

 into the carotid or crural artery towards the heart, or by com- 

 pressing the aorta. The aorta may be either compressed by the 

 thumb of the operator, or by a narrow pad of cork laid over it 

 and pressed upon it by a tourniquet, of which the strap has been 

 passed round the animal's body. 



Mode of Counting the Beats of the Heart. — Now, if we wash to 

 determine the blood-pressure at the same time with the pulse- 

 rate, we may count the latter from the oscillations which each 

 beat of the heart produces in the tracing of the kymographion, 

 or from the sphygmoscope attached to it ; but this is not always 

 necessary, and we may wish to ascertain the pulse-rate without 

 going to the trouble of opening an artery and using a manometer, 

 We may do this in three ways ; — 1'. By feeling the pulse in one 

 of the large arteries, such as the crural, with the finger ; 2. By 

 listening to the beats of the heart with a stethoscope ; 3. By the 

 motion of a needle stuck into the ventricles. For this purpose 

 a fine harelip-needle is inserted at the point where the apex 

 beats, and is pushed upwards into the substance of the ven- 

 tricle. At its upper end it may have either a knob, or a loop to 

 which a thread can be attached, and a barb at the point will 

 prevent it from changing its position in the heart when traction 

 is made upon it. In rabbits, the point where the needle should 

 be inserted is in about half an inch to the left of the sternum 

 in the third intercostal space, and the length of the needle used 

 should be about 3 inches. Various means have been proposed 

 for counting the oscillations more readily than can be done by 

 simply watching the movements of the needle itself. The 

 knob of the needle may be allowed to strike against a wine- 

 glass, and the pulsations may thus be counted by the ear ; or a 

 needle without a knob may be used, and a rice-straw with a 

 piece of bright-coloured paper attached to it may be slipped 

 over it, so that its vibrations, amplified by the long straw, and 

 made more visible by the bright-coloured paper, may be readily 

 counted by the eye. 



A convenient way of registering the oscillations on an upright 



